What is the theme of four sisters by Charles Dickens?

There is no Dickens novel titled "Four Sisters". Perhaps you are thinking of another work? If you can provide more information, I may be able to help.

If you are interested in novels by Charles Dickens featuring sisters, you might be thinking of:

* Great Expectations: The story features the orphaned protagonist Pip and his two elder sisters, Mrs. Joe Gargery and Miss Havisham.

* Bleak House: The novel includes several sisters, most notably the sisters Ada Clare and her cousin, Lady Dedlock.

* Little Dorrit: The story revolves around the family of the imprisoned William Dorrit, and includes his daughters Amy and Fanny.

Please provide more context so I can help you understand the theme of the novel you're thinking of.